Frequency-translating circuits



2 Sheets-Shea 1 Y Oct 9, 1928.

E. PETERSON FREQUENCY TRANSLATING CIRCUITS a w K44 m m F WW QJW w W a W l H HIE M Oct. 9, 1928. 1,687,225

5. PETERSON FREQUENCY TRANSLATING CIRCUITS Filed Janu29, 1927 2 Sheets-Sheeh 2 //Ive/7/br.' [age/7e Pare/son by i- W Af/oczgj Patented Oct. 9, 1928.

llhil'lfE STATES,

PATENT oFFice.

EUGENE PETERSON, o'rNnw YORK, N. Y.; ASSIGNOR T WESTERN ELECTRIC CGMPAEY, INCORPORATED, on NEW YORK, N. Y., A CORPORATION on NEW YORK.

FREQUENCY-TRANSLATING CIRCUITS;

This invention relates to frequency translating circuits and particular to such circuits employing electric discharge devices in the input circuits of which thefrequency translation takes place, as, for example, grid circuit modulation in the grid circuit of a three-electrode vacuum tube, and is a continuation in part of application Serial No. 696,766, filed March 4, 1924.

An object of the invention is to improve the efficiency of frequency translating circuits.

Frequency translating circuits, which are defined for the purpose of this specification as including both modulators and demodulators or detectors, may employ electric discharge devices for performing the frequency'translation function in which case they may be divided into two main types: the input circuit frequency translation, or, as more commonly known, the grid current modulation,

type, in which the combination is produced in the grid or input current circuit and is due to the curvature of the grid current characteristic; and the output current frequency translation, or, as more commonly known, the plate current modulation, type, in which the combination is produced in the plate or output circuit and is due to the curvature of the plate current characteristic.

The products resulting from these two types of modulation or detection may be of opposite phase so that it is often desirable to suppress or prevent one type of modulation when. the other is being used to produce a useful output product.

When input current modulation or detec-. tion is used for producing the useful output products, the discharge device acts as an amplifier for the modulation products produced in the input circuit.

products. H Another feature of this invention is a air-- cuit arrangement for giving the input circuit However, the discharge device may operate also to transmit Application filed January 29, 1927. Serial No. 164,418.

an impedance which is high for the input current modulation or detection products so that they may be efficiently amplified.

Another feature of the invention is a reactive impedance arrangement for differentially dividing'the potential between the discharge device and the external circuit during opposite half cycles to produce input current modulation or detection.

In one embodiment of the invention output current modulation or detection is prevented by introducing into the plate circuit, carrier or signal waves which are of opposite phase to those transmitted through the discharge device. This arrangement in effect increases the impedance of the plate circuit to the carrier or signal waves.

In a preferred embodiment the impedance of the input circuit of a push-pull modulator is increased for the input current modulation or detection products by including a retard coil in each 'of the series arms. Another method of obtaining the same result is to include in the input circuit a filter or other network having a high impedance to these products.

The invention is illustrated in the drawing in which:

Fig. 1 shows one embodiment of the invention employing a filter in the input circuit;

Figs. 2 and 3 show embodiments of the invention employing arrangements for introducing out of phase carrier waves into the output circuit; I

Fig. 4 shows an embodiment of the invention in a push-pull modulator circuit; and

Fig. 5 shows an embodiment of the invention employing a retard coil in the input circuit for increasing the amplification efficiency of the discharge devices.

Fig. 1 shows a frequency translating circuit for combining waves from a signal source with carrier waves from a source 11. The

' combination is effected by means of an electric discharge device 12 which is provided with an input transformer 13and an output transformer 14. The signal source 10 is connected through a transformer 15 to the input terminals of a low pass filter 16. The carrier source 11 is connected to the input terminals of a high pass filter 17 The out-put terminals of filters 16 and 17 are connected inseries to the primary windin of the in ut transformer 13. The filter 16 is designe to freely pass all waves of frequencies within the range of signals produced by the source 10, and to attenuate waves of frequencies above this range, particularly those of the cut-off frequency, including the frequency. of

the carrier wave ed o the source 11, and to attenuate a u substantially suppress Waves of lower frequencies particularly those of the frequencies produced by the signal source 10.

The waves froin the two sources and 11 are combined in the input circuit of the do vice 12 to produce gr d current modulation products in the manner described in the above mentioned application, Serial No. (596,766, by including in the input circuit of the device an impedance of such value that, when the control electrode is driven positive, the greater part of the potential dro p takes place across this im as ice, while during the negative portion of the cycle, the potential di vidcs between the device and the impedance T he input transformer 13 is so designed that its secondary winding serves as this impedance. These grid current modulation prot nets are amplified by the device 12 and trans mitted to the load circuit through the out-put transformer 1 A filter may be connected to the secondary winding of transformer 1% for select ng the waves desired and suppressing others. A filter or netw 18 is connected between the secondary winding of the input transformer 13 and the device 12 for improving the modulation characteristics of the circuit.

This filter is designed to freely transmit waves from the two sources 10 and 11, and to have an output impedance which is high at the frequencies of the grid current modulation products so that the impedance of the circuit COilIlGCLQtl to the control electrode and cathode is high at these frequencies to cause their efficient amplification by the device 12.

In Fig. 2, there is shown a discharge device 20, arranged to operate in a similar manner to'the deviceof Fig. 1 to produce grid current modulation or detection. The signal waves are impressed on the input circuit through an input transformer 21 and carrier waves are impressed on the input circuit through the secondary winding 22 of a hybrid coil or balanced transformer 23. A carrier source 2 1- is connected to the hybrid coil for supplying waves, and has its impedance balanced by the network 25. The remaining terminals of the hybrid coil are connected through the network 26 to the primary winding of a transformer 27, the secondary winding of which is connected in the output circuit of the device in series with the primary Winding of the output transformer 28. By means of this arrangement, a carrier wave is impressed directly on the output circuit of the device 20. By properly poling thetransmitted through the tube 20, and by adjusting the amplitude of the waves by means of the network 26, the net amplitude of the carrier in the output circuit may be made negligibly small, thus preventing plate current modulation. This arrangement, in effect, increases the impedance of the output circuit to the carrier frequency. The network 26' may be a pure resistance network and used only for controlling the amplitude of the waves transmitted therethrough or it may be desirable to design this network to have phase shifting properties to control the phase of the waves.

In the circuit of Fig. 3, an auxiliary discharge device 81 is arranged. to performa function similar to that of the hybrid coil of Fig. 2. The input electrodes of this device and the input electrodes of the modulating tube 30 are connected to a source of carrier waves 32 through the contacts of an adjustable resistance 83. Signal currents are supplied to the input circuit of the device 30 through an input transformer 3 L. faves in the output circuit of the device 30 are transmitted to the load circuit through an output transformer 86. The amplified carrier wave in the output of the auxiliary device 31 is impressed upon the output circuit of the device 30 through a transformer 35, so as to be of opposite phase to the carrier wave transmitted through the device 30. By adjusting the contacts of the resistance 33, the amplitude of this carrier wave may be made such as to practically .annul the effect of the carrier transmitted through the device 30.

Fig. 4 shows a translating circuit, employing two discharge devices and 41 connected in push-pull. relation through an input transformer 42 and an output transformer 43; Signal waves are supplied to the input circuit through a hybrid coil 4a, which has an impedance element 45 connected thereto for balancing the impedance of'the signaling circuit connected to the input. terminals to. The remaining terminals of the hybrid coil are connected through leads t? and adjustable pedance network 53 to the secondary Winding of the outputtransformer 4:3, for introducing into the output circuit a signal wave of opposite phase to that transmitted through the devices 40 and. 41. The network 53 may be pure resistance network and used only for controlling the amplitude of the waves trans mitted therethrou gh or it maybe desirable to design this network to have phase shifting properties to control the phase of the waves.

A carrier wave is supplied to the input circuit from the source 48 through a transformer 49 connected in the common input lead. A network or, filter 50 is connected in the input circuit between the transformer s2 and the Ill? control electrodes of'the devices 40 and 41 for improving the modulationcharacteristic Connected in the common output lead through a transformer 51 is a networlr52 de-' to have an impedance which is high to the carrier wave so as toaid in the 'suppression of plat current modulation.

Grid current modulation or. detection is produced in the inputcircuits of the devices 40 and il in a similar manner as in the cirthe signal in the output circuit is reduced and.

by the net work 52 by which the impedance of the output circuit to c wave is increased.

Fig. 5 shows a translating circuit employing two discharge devices 56 and 57 connected in push-pull relation between the input transformer 58 and output transformer 59.. Signal waves are impressed upon the input circuit through the input transformer 58.

Carrier waves from source 60 are impressed through a transformer 61 connected in the common input lead. Grid current modulation is produced as in the arrangements of the preceding figures. The windings 62- and 68 of a retard coil are connected in series with the secondary winding of the input transformer 58, for increasing the inputimpedance of devices 56 and 5? to the modulation products to cause their efficient ampliflcation'.v Since these -windings are in parallel opposing relation for the carrier wave, they have no effect on the input circuit from that standpoint.

in the common input type of push-pull circuit where both carrier and signal waves are applied through the input transformer (58) a similar result may he obtained by the use of a retard coil in the common cathode lead.

V] hat is claimed is:

1. A frequency translating circuit comprising an electric discharge device, input and output circuits therefor tending to produce frequency translation due to current flow through said device in both of said circuits,

and means for efiectively preventing frequency translation in one of said circuits.

2. A frequency translating circuit comprising an. electric discharge device, input and output circuits therefor, means for supplying waves of different characteristics to said input circuit to produce input current frequency translation, and means for preventing output current frequency translation. I

3. A frequency translating circuit'comprising an electric discharge device, input and output circuits therefor, means for supplying waves of different characteristics to said input circuit to produce input current fre quency.translation, and means in sald output circuit for preventing output current .fre-

quency translation.- I

r f. A frequency translating circuit compri mg an electric discharge device, input and output circuits therefor, means for supplying waves ofdiiferent characteristics to said input circuit to produce input current frequencytranslation, and means for effectively giving said output circuit a high impedance to at least one of said waves to prevent output cu rent frequency translation.

5. A frequency translating circuit accord ing to the preceding claim in which said last mentioned means effectively gives said output circuit a high impedance to both of said waves. I

6. 'A frequency translating circuit comprising an electric discharge device, input and output circuits therefor, means for impressing waves of different frequency characteristics on said input circuit to produce input current frequency ranslation, and means for. impressing upon the output circuit awave of the same fre ,uency' characteristics as one of the waves impressed on the input circuit hut in outof-phase relation to the corresponding wave transmitted by said device, to prevent output current frequency translation.

7. A frequency translating circuit comprising an electric discharge device, inputand output circuitstherefor, a source of signal waves, means for impressing waves from said source upon said input circuit, a source of carrier waves, means for impressing waves from said source upon said input circuit to produce with said signaling waves modulation or detection products due to current in said input circuit, and means for impressing waves from said source of signal waves upon said output circuit in out-of-phase relation to the corresponding waves transmitted by said device.

8. A frequency translating circuit comprising an electric discharge device, input and output circuits therefor, means for supplying waves of different characteristics tosaid input circuit to produce input current frequency translation, and means for substan-' 7 having a high impedance to the modulation or detection products to cause them to be efficiently amplified by saiddevice.

on i

l i i 10. A frequency translating circuit comprising an electric discharge device, input and output circuits therefor, means for impressing Waves of different characteristics upon said input circuit to produce input cure rent frequency translation and an impedance net-Work connected in said input circuit, said network having an input impedance which is high at the frequencies of said Waves and an output impedance which is high at the frequencies of the modulation or detection products.

11. A frequency translating circuit comprising an electric discharge device, input and output circuits erefor, and means for impressing Waves of different characteristics upon said input circuit, said means having a reactive impedance value such that during opposite half cycles the potential is differentially divided between the device and the external circuit to produce input current frequency translation.

12. A frequency translating circuit comprising an electric discharge device, input and output circuits'therefer, anc means for impressing Waves of different characteristics upon said input circuit, said means including a transformer having a secondary Winding of impedance such that during opposite half cycles the potential is differentially divided between the device and the external circuit to. produce input current frequency translation. 7

13. A frequency translating circuit comprising an electric discharge device, input and output circuits therefor, means for impressing Waves of different characteristics upon said input circuit to produce input current frequency translation, and inductive meansin the input circuit having a high impedance to the input current modulation or detection products to causethein to be efli-,

ciently amplified. I 1

14. A frequency translating circuit comprising a pair of electric discharge devices connected in push-pull relation, means for impressing Waves of different characteristics upon the input circuit to produce input current frequency translation, and inductive means in the input circuit having a high impedance to the modulation or detection prod ucts and a low impedance to the component Waves.

.15. A frequency translating circuit comprising an electric discharge device, input and output circuits therefore, a source of signal Waves, a source of carrier Waves, means for impressing Waves from one of said sources upon the input circuit and a balanced circuit arrangen'ient for impressing Waves from said other source upon both the input and output circuits Without interact-ion therebetWeen, the Waves from said sources being combined in the input circuit to produce input current modulation or detection products and the Waves from said other source impressed upon the output circuit being in out of phase relation to the corresponding Waves transmitted by the device to prevent output current frequency translation.

In Witness whereof, I hereuntosubscribe my name this 27th day of January. A. D..

EUGENE PETERSON. 

